In the 14th and 15th centuries, the Habsburgs began to accumulate other provinces in the vicinity of the Duchy of Austria. In 1438, Duke Albert V of Austria was chosen as the successor to his father-in-law, Emperor Sigismund. Although Albert himself only reigned for a year, from then on, every emperor of the Holy Roman Empire was a Habsburg, with only one exception.

The Habsburgs began also to accumulate lands far from the Hereditary Lands. In 1477, Archduke Maximilian, only son of Emperor Frederick III, married the heiress Maria of Burgundy, thus acquiring most of the Low Countries for the family.[13][14] His son Philip the Fair married the heiress of Castile and Aragon, and thus acquired Spain and its Italian, African, and New World appendages for the Habsburgs.

In 1526, following the Battle of Mohács, Austrian rulers expanded their territories, bringing Bohemia and the part of Hungary not occupied by the Ottomans under their rule. Ottoman expansion into Hungary led to frequent conflicts between the two powers, particularly evident in the so-called Long War of 1593 to 1606.